Transcript Astronomy

In This Lesson:
Unit 1
The Scale of the
Universe
(Lesson 1 of 2)
Today is Monday,
th
April 11 , 2016
Pre-Class:
What is astronomy?
Put your syllabus receipts in the Turn-In Box. 
http://apod.nasa.gov/apod/image/0708/M67_Greg_Noel.jpg
Messier 67 (M67) Star Cluster (at center)
Today’s Agenda
•
•
•
•
Astronomy Pre-Test.
The Scale of the Universe.
Scientific Notation.
Really long distances.
• Where is this in my book?
– Pages 6-15.
By the end of this lesson…
• You should be able to describe measurements
in scientific notation.
• You should be able to measure astronomical
distances in three units.
Astronomy Pre-Test
• Before we start this class, I’d like to know what
you know.
• Do your best on this pre-test, but it won’t
affect your grade.
– You’ll also be the one grading it.
• Once you complete all questions, put your
pencil down.
What is astronomy?
• Astronomy seeks to
understand the
structure and evolution
of the physical universe.
• Doing so also helps us
to understand the origin
of life in the universe.
http://apod.nasa.gov/apod/image/0708/m17x800ignacio.jpg
Messier 17 (M17) Nebula
Perspective
• Ever looked at the stars at night?
– There are about 6000 “celestial objects” visible
with the naked eye from somewhere on Earth.
– Pennsylvania gets a view of about 75% of the sky
throughout the year, so you can see about 4500
objects.
– Of the 4500 visible objects from PA, only 7 objects
are not stars.
Perspective
Visible Objects That Aren’t Stars
•
•
•
•
•
•
•
The Moon
Mars
Jupiter
Saturn
Venus
Mercury
The Andromeda Galaxy
Galaxies and Stars
• Now might be a good time to tell you that a
galaxy is different from a constellation.
– A constellation is a relatively small group of stars that
can be connected with lines to make a shape.
• Like a crab or a goat or something.
– A galaxy is a large group of stars (on average 400
billion) that you really don’t connect.
• Because it would look like the Mona Lisa, if painted by a
two-year-old amputee.
– Need I remind you that our own galaxy is known as
the Milky Way?
Perspective
• So, that makes us a very small part of the universe.
• Want some more perspective?
– The Scale of the Universe
– Scale of the Universe.lnk
• Want even more perspective?
– Cosmos – Our Cosmic Address
• FYI, you probably already know this, but
“everything” is known as the universe.
– The universe is about 13.8 billion years old, which is kinda
hard to wrap your head around. For some help:
– Cosmos – Cosmic Calendar
Scales
• Perhaps the most important thing to know going
into astronomy is how things are measured.
• Simply put, celestial bodies are so ginormous
that it’s difficult to measure things.
• We’ll learn a lot of the measurements
throughout the course, but we’ll start with two
important things:
– Scientific Notation (in general).
– The Light Year, the Parsec, and the Astronomical Unit.
I get it…now what?
• Numbers written in scientific notation take this
form:
• M x 10n
– M is between 1 and 10 (1 or above, less than 10).
• M is sometimes called the mantissa or significand.
– n is an integer.
• This allows you to take measurements of either
extremely large or extremely small numbers.
– In our case, mainly extremely large.
2,500,000,000
Converting
to Scientific .Notation
9 8 7 6 5 4 3 2 1
• Make 2,500,000,000 into scientific notation.
– Step 1: Put in an understood decimal point.
– Step 2: Decide where the decimal point must end up so
that there is only one nonzero digit to its left (M).
– Step 3: Count how many places you have to bounce the
decimal point to get there (n).
– Step 4: Rewrite in the M x 10n form.
2.5 x
9
10
Converting0.0000579
to Scientific Notation
123 4 5
• Make 0.0000579 into scientific notation.
– Step 1: Put in an understood decimal point (already
done).
– Step 2: Decide where the decimal point must end up so
that there is only one nonzero digit to its left (M).
– Step 3: Count how many places you have to bounce the
decimal point to get there (n).
– Step 4: Rewrite in the M x 10n form.
-5
5.79 x 10
Practice
• Scientific Notation worksheet
– Try #1-12.
Scientific Notation
• Remember that moving the decimal point left
makes n go up by one; moving it right makes it
go down by one.
• Since you now know how to write in scientific
notation, let’s talk about how to calculate in
scientific notation.
• We’ll start with addition and subtraction.
Addition and Subtraction
• If the exponents are the
same, simply add or
subtract the (M) numbers
in front and leave the x 10n
part unchanged.
• You can do this for
addition or subtraction.
4 x 106
+ 3 x 106
7 x 106
4 x 106
- 3 x 106
1 x 106
•
Addition and Subtraction
6
4 x 10
If the exponents are not
5
+ 3 x 10
the same, we have to
move a decimal point until
they are.
• Move the decimal on the
smaller number!
4.00 x 106
+ 3.00 x 105
4.00 x 106
+ 0.30 x 106
6
4.3 x 10
Practice
• Solve the following in scientific notation:
2.37 x 10-6
+ 3.48 x 10-4
-6
2.37 x 10-4
0.0237
+ 3.48 x 10-4
3.5037 x 10-4
Multiplication and Division
• For multiplication, just
multiply the digits in front
(M), then add the
exponents (n).
• Remember that you still
need to make sure the
number in front (M) is
between 1 and 10.
8 x 103
x 3 x 109
24 x 1012
13
2.4 x 10
Multiplication and Division
• For division, do the opposite of multiplication.
• Just divide the digits in front (M), then
subtract the exponents (n).
6x
8
10
/2x
7
10
= 3x
30
1
10
Practice
• Solve the following in scientific notation:
2 x 10-2 / 5 x 10-6 = 0.4 x 104
3
4.0 x 10
One final note…
• You may notice your calculator giving you
answers like this:
• 5.665 E 8
• 5.665 8
• In both cases, your calculator is trying to say:
• 5.665 x 108
Practice
• Scientific Notation worksheet
– Try #1-5 (lower section).
• Now to challenge yourself:
– Try the back, odd numbers only.
– Stuck? Ask.
Other
Scientific
Notationworthy
Measurements
The Units of Astronomy
• There are several important astronomical
units out there, one of which we’ll be focusing
on now. Here are the big three:
– The light year.
– The parsec.
– The astronomical unit.
• Let’s define them in reverse.
The Units of Astronomy
Astronomical Units
• An astronomical unit (au) is a very large distance
used to describe space stuff.
– Cause space is, you know, big.
• It was originally defined as the distance between
the Earth and the Sun, but there’s a problem.
– The Earth and the Sun are not always the same
distance apart.
• So, the official designation of the au is:
– 149,597,870,690 meters
• That’s about 150,000,000 km or 93,000,000 miles.
The Units of Astronomy
Astronomical Units
• For perspective, if the Earth were a ping pong
ball…
• …the Sun would be about 9 feet across…
• …and located around 900 feet away.
• That’s an astronomical unit!
The Units of Astronomy
Parsecs
• A parsec (pc) is 3.26 light years (more in a moment),
or 3.086 x 1016 m…but it’s a little bit more
complicated than that.
• The term comes from “parallax” and “arcsecond,”
which are both terms used to measure the movement
of celestial objects against a background.
• Let’s see if we can learn a little more:
– UniverseToday – What is a Parsec?
• You should understand the concept of a parsec, but
don’t worry about how to calculate it.
http://www.universetoday.com/32872/parsec/
About Parallax
• In short, parallax is the idea that objects may
appear to “move” based on the position of the
observer.
– For example, imagine looking at any two other desks
in this room.
• The left one’s on the left, the right one’s on the right.
– Walk to the other side of those desks, though, and
sudden the one that was on the left is on the right,
and vice versa.
• That’s parallax.
Parsecs and Parallax
• Parsecs attempt to quantify
the distance to a celestial
object by using parallax.
• Once you get the parallax
“distance” (seconds), you
can use trigonometry to
calculate the distance to
the object.
– Effectively, you do
triangulation.
– But how do you get the
parallax distance?
Arcminutes and Arcseconds
• To help map out the sky,
astronomers divide the entire
celestial sphere into 360 equal
slices (360 degrees).
– Each 1° of sky is 60 arcminutes.
– Each arcminute is made of 60
arcseconds.
– So an arcsecond is 1/60 of an
arcminute, or 1/3600 of a
degree.
• The sec of arcsecond and the par of
parallax is where we get parsec.
Parsecs
• Pythagoras would be
proud!
Stellar Parallax
• Stellar Parallax Interactive
The Units of Astronomy
Light Years
• A light year (ly) is the distance light travels in a
year (in a vacuum).
• NOT A TIME UNIT!
• Light travels at 186,282.397 miles per second, or
2.998 x 108 m/sec.
• As you might guess, light is so fast that a light year
is a REALLY LONG DISTANCE.
– It’s 62,239.72 au, but there’s something even cooler.
• Let’s look at this with an example.
The Units of Astronomy
Light Years
• Which comes first, thunder or lightning?
– Lightning, but technically only by an instant.
• Lightning is so hot that it causes the air around it to
rapidly expand and move faster.
– All those air molecules hitting one another causes
thunder.
• The thing is, if you’re far from the impact point, it
could take a few seconds to hear thunder after
seeing lightning.
– Sound takes about 5 seconds to travel one mile through
air, so if it takes (for example) 10 seconds to hear thunder
after a lightning bolt, you know the strike was 2 miles
away…approximately.
The Units of Astronomy
Light Years
• You may also experience this in a big building like a
stadium.
• During baseball games, you might see the bat hit the
ball, but you don’t hear the sound for a second or two.
– Since light travels so much faster than sound, by the time it
gets to you it looks “out of sync.”
http://www.stadiumpage.com/stpages/Shea_Upper.html
The Units of Astronomy
Light Years
• It’s important to remember that light does not
move instantaneously.
• It just seems that way here on Earth, across
relatively very small distances.
• However, because it takes a few moments to
reach your eye, technically, you are always…
• …LOOKING BACK IN TIME!
• For more, let’s revisit UniverseToday.
The Units of Astronomy
Light Years
• Yet another example:
– In July of 1054, Chinese,
Japanese, Korean, and Arab
astronomers reported seeing a
“star” appear in the sky that
was so bright it was visible in
daylight.
– We now know it was the
explosion from a supernova
that created M1, the Crab
Nebula.
https://upload.wikimedia.org/wikipedia/commons/0/0f/CrabNebulaH
ubble.jpg
http://chandra.harvard.edu/chronicle/0406/historical_snr/SupernovaCina.jpg
The Units of Astronomy
Light Years
• The Crab Nebula is 5000 light
years away from Earth.
• Therefore, even though
astronomers recorded the
event as “happening” in 1054,
in reality the event occurred
5000 years prior (~3946 BC).
https://upload.wikimedia.org/wikipedia/commons/0/0f/CrabNebulaH
ubble.jpg
http://chandra.harvard.edu/chronicle/0406/historical_snr/SupernovaCina.jpg
The Units of Astronomy
Light Years
• Now to put that knowledge to practice.
• Let’s get a sense for how far a light year is.
– How Long is a Light Year worksheet
Other Methods of Scaling
• So light years, parsecs, and astronomical units
are all units of distance.
• Parallax is a method of measuring that can be
converted to those units of distance above.
• There’s one problem, though:
– Parallax only works for objects that are, well,
relatively close.
– Here are some alternate methods along with
sample celestial bodies.
Aside: Space-Time
• You might be aware of a somewhat similar
phenomenon called “space-time.”
• In short, the part of it you’re thinking of is the
idea that time passes at different rates based
on gravity.
• You might have even seen a movie dealing
with the concept of space-time as a central
plot point…
Maybe you remember this?
Aside: Space-Time
• Space-time isn’t something within the scope of this course
(more a physics thing), but here’s your brief summary
anyway:
– Space-time is the idea that “time” is not separate from space.
• In other words, it’s a little like adding “time” to a coordinate system that
also features latitude and longitude.
• Space-time is therefore a four-dimensional object.
– Einstein’s Theory of Relativity does much to explain the idea of
space-time.
– According to Relativity, time passes more slowly in high-gravity
areas like places near black holes.
http://www.space.com/27692-science-of-interstellar-infographic.html
Closure
• From this lesson, I hope you take something
rather important away:
– A frame of mind.
• Throughout this course (and your life), try to
remember that the universe is so big that it’s
nearly impossible for humans to actually
perceive all of it.
Closure
• Look up and realize that, in the direction
you’re looking, the universe goes on…
• …and on…
• …and on…
• …virtually forever. Until you get to a point so
far away that no signals from it have yet even
reached us, making it truly “non-observable.”
– The Scale of the Universe one more time…
– Scale of the Universe.lnk
Closure – One Last Thing
• Let’s play a little game called “Small/Large and
Near/Far.”
• Credit where credit’s due:
– This comes from Cherilynn Morrow, Ph.D., at the
University of Colorado.
Small/Large and Near/Far
• Get a scrap piece of paper and make two
columns:
Smallest
Small/Large
Near/Far
1.
1.
2.
2.
3.
3.
4.
4.
5.
5.
6.
6.
7.
7.
8.
8.
Largest 9.
9.
Nearest
Farthest
Small/Large
• On the next slide you’ll see nine
images/objects/things.
• Using the left column, rank them from the
smallest to largest object.
• Write the letter of the object and the name.
• If anyone gets all nine correct in order, s/he
will win 500 imaginary bonus points.
A. The Sun
B. Earth
D. The Moon
E. The Solar System
G. Mars
H. Galaxy
C. Space Shuttle
F. Bears
I. Jupiter
Small/Large: Solution
1. F. Bears
2. C. Space Shuttle
3. D. The Moon
4. G. Mars
5. B. Earth
6. I. Jupiter
7. A. The Sun
8. E. The Solar System
9. H. Galaxy
Near/Far
• On the next slide you’ll see nine
images/objects/things.
• Using the right column, rank them from the
“nearest to Earth” to “farthest from Earth.”
• Write the letter of the object and the name.
• If anyone gets all nine correct in order, s/he will
also win 500 imaginary bonus points.
– So you could get 1000 imaginary bonus points total!
A. The Sun
B. Galaxy
D. The Moon
E. Jet Airplane
G. Eagle
H. Stars of Ursa Major
C. Aurora Borealis
F. The Hubble Telescope
I. Saturn
Near/Far: Solution
1. G. Eagle
4. F. The Hubble Telescope
7. I. Saturn
2. E. Jet Airplane
3. C. Aurora Borealis
5. D. The Moon
6. A. The Sun
8. H. Stars of Ursa Major
9. B. Galaxy
Near/Far: Solution Notes
2. Jet airplanes typically fly in the stratosphere (more
than 10 km/6 mi up).
3. Auroras occur at the highest reaches of the
atmosphere (95-190 km/60-120 mi).
4. The Hubble Telescope is 600 km/373 mi away.
5. The Moon is 400,000 km/250,000 mi.
6. The Sun is 1 au (150,000,000 km/93,000,000 mi).
7. Saturn is between 9 au and 11 au away.
8. Stars of Ursa Major (the Big Dipper) are at least 70100 light years away (the closest ones).
9. NGC 4414 (Galaxy) is 60 million light years away (you
can’t get an image like that of our own galaxy).
Closure
• How Do We Measure Distance In The Universe?
Other Closure Videos
UniverseToday
•
•
•
•
•
•
•
•
How Far Can You See In The Universe?
How Long Does It Take Sunlight to Reach Earth?
Are Aliens Watching Old TV Shows?
How Big is the Solar System?
How Big is the Universe?
How Far is the Earth from the Sun?
How Long Does it Take Sunlight to Reach Earth?
What is the Distance to the Moon?
Closure
• Looking Out is Looking Back
Hyperspace
• Star Stuff
• Are We Alone?